The invention relates to a method for manufacturing of a high temperature superconductor (=HTS) coated tape, with the following steps:
a) preparation of a substrate tape,
b) deposition of at least one buffer layer,
c) deposition of an HTS film,
d) deposition of a metallic protection layer on the HTS film,
e) deposition of a metallic shunt layer.
A layered HTS structure, comprising a substrate, a buffer layer, an HTS layer, a capping layer and a stabilizer layer, or a corresponding method for its manufacturing, respectively, are known from U.S. Pat. No. 7,774,035 B2.
The invention deals with methods for manufacturing of high temperature superconducting (HTS) coated tapes and may be employed, in particular, in the fields of building of motors, magnets, generators, energy transmission and energy distribution.
Superconductors are used when large electric currents shall be transported or applied with low ohmic losses. High temperature superconductors, having a critical temperature high enough such that cooling may be done with liquid nitrogen (boiling point at atmospheric pressure about 77K), are inexpensive in cooling. However, due to their ceramic properties, HTS devices are usually manufactured on substrates (HTS coated conductors); in particular, there are tape type substrates that typically offer some mechanical flexibility to HTS coated conductors. For HTS coated tapes, it is known to deposit the HTS film on a buffer layer deposited on the substrate, in order to achieve a beneficial HTS grain orientation needed for high critical currents. The HTS film is typically covered by a protection layer (also called capping layer) of a noble metal in order to avoid corrosion, and a shunt layer (also called stabilization layer) is deposited on top.
A cutting of HTS coated conductors is needed in many application segments e.g. for manufacturing of planar electrical circuits, de-coupled filaments, HF inductances, etc.
Generally, cutting techniques known from semiconductor technology may be used with HTS coated conductors. For example, water jet techniques (also combined with gas streams) are known from DE 44 18 845 C1, EP 0 375 578 A1 or US 2007/0278195 A1. Further known methods are electro-erosion or mechanical slitting.
However, when applying these techniques to HTS coated conductors, partial or complete damage of the HTS structure results. To the inventor's knowledge, this is caused via a spreading the damage area outside the “treated” area, what may be caused in some cases by spreading of cracks, or the penetration of liquids or vapours which are aggressive regarding the HTS or buffer layers. Such deterioration results in a severe reduction of the overall critical current (with a deterioration degree depending on materials employed) and a decrease in the critical temperature of the HTS film.
It is also known to cut workpieces such as silicon wafers by means of a laser beam, in particular in combination with liquid flow, compare U.S. Pat. No. 7,728,258 B2 or Even when applying laser beam cutting, HTS coated conductors are subject to a considerable deterioration of their critical currents due to the cutting.
US 2008/0113870 A1 describes a laser beam cutting process for preparing metal filaments. HTS material and a metallic protection layer are deposited on the prepared metal filaments subsequently.
It is the object of the invention to reduce the loss of the critical current and to reduce or avoid a deterioration of the critical temperature in a HTS coated tape due to tape cutting.